1. Field of the Invention
The present invention relates to the field of motorcycle lubrication oil cooling systems.
2. Description of the Related Art
Since engines include many internal sliding parts and rotating parts, they are designed to function fully by decreasing friction between these parts by providing lubrication oil to lubricate these parts by a lubrication system.
Some lubrication systems have means to cool lubrication oil since lubrication oil loses its lubrication capability when its temperature rises.
When the temperature rise of lubrication oil is relatively small, such as in the case of low speed engines, there are means to prevent the lubrication oil temperature from rising by improving heat release characteristics by increasing the contact surface area between the lubrication oil and the outside air by providing an oil pan and oil tank.
On the other hand, for high speed engines, in which the lubrication oil temperature rise is relatively large requiring active cooling, it has been a general practice to provide an oil cooler to prevent the temperature of lubrication oil from rising.
For example, many oil coolers mounted on motorcycles are of a lightweight and simple construction of an air-cooled type. Yet, since the air cooled-type has limitations in terms of installation location (its full function cannot be utilized unless it is positioned to receive airflow caused by driving). In the case when the engine is water-cooled, some engines are equipped with a water-cooled oil cooler as indicated in Japanese Patent Application Laid-Open (Kokai) H5-131962.
If an oil cooler is provided to achieve a cooling performance beyond what is obtainable by providing an oil pan or an oil tank, the number of parts and the number of assembly process steps involved in piping, etc. will increase over and above what is required for the main oil cooler body. Even for the air-cooled type, a weight increase is unavoidable.
In addition, there are other difficulties resulting from the increase in potential oil leak locations, since the main body of the oil cooler and engine are connected by piping.
There is also a large difference in terms of engine cooling performance, cost, and weight between the systems with and without an oil cooler. There has been no technology to achieve a cooling performance, which is more than what is achieved by providing an oil pan or an oil tank, yet less than what can be achieved by an oil cooler.